Simple Adaptive Control of a Satellite with Large Flexible Appendages

Abstract

Larger power requirements from modern spacecraft precipitate Brobdingnagian solararrays to fulfil budgetary needs. Although the solar arrays may have a relatively small influence on the total mass of the spacecraft system, large arrays with long flexible panels do affect the dynamics through the moment of inertia. Therefore, this paper examines the combination of a control system that has been verified for rigid-body satellite control with a flexible solarpanel system. The control system design is based on simple adaptive control theory, and uses a stabilised, linear reference model to aid in driving the plant output error to zero and hence achieving a commanded attitude. The rigid body-elastic body coupling in simulation has been investigated using a finite element description with Lagrange multipliers as force constraints. Responses of the rigid satellite and with the flexible solar array are compared for 1_ step commands, both for a single axis and all three combined. The coupled dynamics increases the controller effort and showed effect of the elastic bodies on the controller system by the deviations from an implementation for a rigid satellite only. A sample investigation of a impulsive force, simulating a particle debris impact, shows the control effort exerted to stabilise the spacecraft. For all simulated cases, the adaptive controller showed a robust performance, despite induced interface moments in the same order of magnitude as the maximum control moments.